Biodegradable Water-Sensitive Films

ABSTRACT

A film that is biodegradable and water-sensitive (e.g., water-soluble, water-dispersible, etc.) in that it loses its integrity over time in the presence of water is provided. The film contains a biodegradable polyester, starch, water-soluble polymer, and plasticizer. The desired water-sensitive attributes of film may be achieved in the present invention by selectively controlling a variety of aspects of the film construction, such as the nature of the components employed, the relative amount of each component, the manner in which the film is formed, and so forth.

BACKGROUND OF THE INVENTION

Films are employed in a wide variety of disposable goods, such asdiapers, sanitary napkins, adult incontinence garments, bandages, etc.For example, many sanitary napkins have an adhesive strip on thebackside of the napkin (the napkin surface opposite to thebody-contacting surface) to affix the napkin to an undergarment and holdthe napkin in place against the body. Before use, the adhesive strip isprotected with a peelable release liner. Once removed, the peelablerelease liner must be discarded. Conventional release liners may containa film or paper coated with a release coating. Such release-coated filmsor papers, however, do not readily disperse in water, and as such,disposal options are limited to depositing the release liner in a trashreceptacle. Although disposing of conventional release liners in atoilet would be convenient to the consumer, it would potentially createblockages in the toilet.

In response to these and other problems, flushable release liners havebeen developed that are formed from a water-sensitive film, U.S. Pat.No. 6,296,914 to Kerins, et al. describes a water-sensitive film thatmay include, for instance, polyethylene oxide, ethylene oxide-propyleneoxide copolymers, polymethacrylic acid, polymethacrylic acid copolymers,polyvinyl alcohol, poly(2-ethyl oxazoline), polyvinyl methyl ether,polyvinyl pyrrolidone/vinyl acetate copolymers, methyl cellulose, ethylcellulose, hydroxypropyl cellulose, hydroxypropyl methyl cellulose,ethyl hydroxyethyl cellulose, methyl ether starch, poly(n-isopropylacrylamide), poly N-vinyl caprolactam, polyvinyl methyl oxazolidone,poly(2-isopropyl-2-oxazoline), poly(2,4-dimethyl-6-triazinyl ethylene),or a combination thereof. Some of these polymers, however, are notthermoplastic and thus are not readily processed using thermoplasticfilm converting equipment. Further, these films are also not generallybiodegradable and may thus further complicate the disposal process.Certain water-sensitive films also tend to lack good mechanicalproperties during use.

As such, a need currently exists for a film that exhibits goodmechanical properties, and is also biodegradable and water-sensitive.

SUMMARY OF THE INVENTION

In accordance with one embodiment of the present invention, awater-sensitive biodegradable film is disclosed that comprises fromabout 1 wt. % to about 50 wt. % of at least one biodegradable polyester,from about 0.5 wt. % to about 45 wt. % of at least one water-sensitivestarch, from about 0.1 wt. % to about 40 wt. % of at least oneplasticizer, and from about 0.1 wt. % to about 40 wt. % of at least onewater-soluble polymer. The biodegradable polyester has a melting pointof from about 50° C. to about 180° C. and a glass transition temperatureof about 25° C. or less.

In accordance with another embodiment of the present invention, anabsorbent article is disclosed that comprises a body portion thatincludes a liquid permeable topsheet, a generally liquid impermeablebacksheet, and an absorbent core positioned between the backsheet andthe topsheet. The absorbent article further comprises a release linerthat defines a first surface and an opposing second surface, the firstsurface being disposed adjacent to an adhesive located on the absorbentarticle. The release liner, the backsheet, or both include awater-sensitive biodegradable film comprising at least one biodegradablepolyester, at least one starch, at least one water-soluble polymer, andat least one plasticizer.

Other features and aspects of the present invention are discussed ingreater detail below.

BRIEF DESCRIPTION OF THE DRAWINGS

A full and enabling disclosure of the present invention, including thebest mode thereof, directed to one of ordinary skill in the art, is setforth more particularly in the remainder of the specification, whichmakes reference to the appended figures in which:

FIG. 1 is a schematic illustration of one embodiment of a method forforming a water-sensitive film in accordance with the present invention;and

FIG. 2 is a top view of an absorbent article that may be formed inaccordance with one embodiment of the present invention.

Repeat use of references characters in the present specification anddrawings is intended to represent same or analogous features or elementsof the invention.

DETAILED DESCRIPTION OF REPRESENTATIVE EMBODIMENTS

Reference now will be made in detail to various embodiments of theinvention, one or more examples of which are set forth below. Eachexample is provided by way of explanation of the invention, notlimitation of the invention. In fact, it will be apparent to thoseskilled in the art that various modifications and variations may be madein the present invention without departing from the scope or spirit ofthe invention. For instance, features illustrated or described as partof one embodiment, may be used on another embodiment to yield a stillfurther embodiment. Thus, it is intended that the present inventioncovers such modifications and variations as come within the scope of theappended claims and their equivalents.

Generally speaking, the present invention is directed to a film that isbiodegradable and water-sensitive (e.g., water-soluble,water-dispersible, etc.) in that it loses its integrity over time in thepresence of water. The film contains a biodegradable polyester, starch,water-soluble polymer, and plasticizer. The desired water-sensitiveattributes of film may be achieved in the present invention byselectively controlling a variety of aspects of the film construction,such as the nature of the components employed, the relative amount ofeach component, the manner in which the film is formed, and so forth. Inthis regard, various embodiments of the present invention will now bedescribed in more detail below.

1. Film Components

A. Biodegradable Polyester

The term “biodegradable” generally refers to a material that degradesfrom the action of naturally occurring microorganisms, such as bacteria,fungi, and algae; environmental heat; moisture; or other environmentalfactors, such as determined according to ASTM Test Method 5338.92. Thebiodegradable polyesters employed in the present invention typicallyhave a relatively low glass transition temperature (“T_(g)”) to reducestiffness of the film and improve the processability of the polymers.For example, the T_(g) may be about 25° C. or less, in some embodimentsabout 0° C. or less, and in some embodiments, about −10° C. or less.Likewise, the melting point of the biodegradable polyesters is alsorelatively low to improve the rate of biodegradation. For example, themelting point is typically from about 50° C. to about 180° C., in someembodiments from about 80° C. to about 160° C., and in some embodiments,from about 100° C. to about 140° C. The melting temperature and glasstransition temperature may be determined using differential scanningcalorimetry (“DSC”) in accordance with ASTM D-3417 as is well known inthe art. Such tests may be employed using a DSC Q100 DifferentialScanning Calorimeter (outfitted with a liquid nitrogen coolingaccessory) and with a THERMAL ADVANTAGE (release 4.6.6) analysissoftware program, which are available from T.A. Instruments Inc. of NewCastle, Del.

The biodegradable polyesters may also have a number average molecularweight (“M_(n)”) ranging from about 40,000 to about 120,000 grams permole, in some embodiments from about 50,000 to about 100,000 grams permole, and in some embodiments, from about 60,000 to about 85,000 gramsper mole. Likewise, the polyesters may also have a weight averagemolecular weight (“M_(w)”) ranging from about 70,000 to about 300,000grams per mole, in some embodiments from about 80,000 to about 200,000grams per mole, and in some embodiments, from about 100,000 to about150,000 grams per mole. The ratio of the weight average molecular weightto the number average molecular weight (“M_(w)/M_(n),”), i.e., the“polydispersity index”, is also relatively low. For example, thepolydispersity index typically ranges from about 1.0 to about 4.0, insome embodiments from about 1.2 to about 3.0, and in some embodiments,from about 1.4 to about 2.0. The weight and number average molecularweights may be determined by methods known to those skilled in the art.

The biodegradable polyesters may also have an apparent viscosity of fromabout 100 to about 1000 Pascal seconds (Pa·s), in some embodiments fromabout 200 to about 800 Pa·s, and in some embodiments, from about 300 toabout 600 Pa·s, as determined at a temperature of 170° C. and a shearrate of 1000 sec¹. The melt flow index of the biodegradable polyestersmay also range from about 0.1 to about 30 grams per 10 minutes, in someembodiments from about 0.5 to about 10 grams per 10 minutes, and in someembodiments, from about 1 to about 5 grams per 10 minutes. The melt flowindex is the weight of a polymer (in grams) that may be forced throughan extrusion rheometer orifice (0.0825-inch diameter) when subjected toa load of 2160 grams in 10 minutes at a certain temperature (e.g., 190°C.), measured in accordance with ASTM Test Method D1238-E.

Of course, the melt flow index of the biodegradable polyesters willultimately depend upon the selected film-forming process. For example,when extruded as a cast film, higher melt flow index polymers aretypically desired, such as about 4 grams per 10 minutes or more, in someembodiments, from about 5 to about 12 grams per 10 minutes, and in someembodiments, from about 7 to about 9 grams per 10 minutes. Likewise,when formed as a blown film, lower melt flow index polymers aretypically desired, such as less than about 12 grams per 10 minutes orless, in some embodiments from about 1 to about 7 grams per 10 minutes,and in some embodiments, from about 2 to about 5 grams per 10 minutes.

Examples of suitable biodegradable polyesters include aliphaticpolyesters, such as polycaprolactone, polyesteramides, modifiedpolyethylene terephthalate, polylactic acid (PLA) and its copolymers,terpolymers based on polylactic acid, polyglycolic acid, polyalkylenecarbonates (such as polyethylene carbonate), polyhydroxyalkanoates(PHA), poly-3-hydroxybutyrate (PHB), poly-3-hydroxyvalerate (PHV),poly-3-hydroxybutyrate-co-4-hydroybutyrate,poly-3-hydroxybutyrate-co-3-hydroxyvalerate copolymers (PHBV),poly-3-hydroxybutyrate-co-3-hydroxyhexanoate,poly-3-hydroxybutyrate-co-3-hydroxyoctanoate,poly-3-hydroxybutyrate-co-3-hydroxydecanoate,poly-3-hydroxybutyrate-co-3-hydroxyoctadecanoate, and succinate-basedaliphatic polymers (e.g., polybutylene succinate, polybutylene succinateadipate, polyethylene succinate, etc.); aromatic polyesters and modifiedaromatic polyesters; and aliphatic-aromatic copolyesters. In oneparticular embodiment, the biodegradable polyester is analiphatic-aromatic copolyester (e.g., block, random, graft, etc.). Thealiphatic-aromatic copolyester may be synthesized using any knowntechnique, such as through the condensation polymerization of a polyolin conjunction with aliphatic and aromatic dicarboxylic acids oranhydrides thereof. The polyols may be substituted or unsubstituted,linear or branched, polyols selected from polyols containing 2 to about12 carbon atoms and polyalkylene ether glycols containing 2 to 8 carbonatoms. Examples of polyols that may be used include, but are not limitedto, ethylene glycol, diethylene glycol, propylene glycol,1,2-propanediol, 1,3-propanediol, 2,2-dimethyl-1,3-propanediol,1,2-butanediol, 1,3-butanediol, 1,4-butanediol, 1,2-pentanediol,1,5-pentanediol, 1,6-hexanediol, polyethylene glycol, diethylene glycol,2,2,4-trimethyl-1,6-hexanediol, thiodiethanol,1,3-cyclohexanedimethanol, 1,4-cyclohexanedimethanol,2,2,4,4-tetramethyl-1,3-cyclobutanediol, cyclopentanediol, triethyleneglycol, and tetraethylene glycol. Preferred polyols include1,4-butanediol; 1,3-propanediol; ethylene glycol; 1,6-hexanediol;diethylene glycol; and 1,4-cyclohexanedimethanol.

Representative aliphatic dicarboxylic acids that may be used includesubstituted or unsubstituted, linear or branched, non-aromaticdicarboxylic acids selected from aliphatic dicarboxylic acids containing1 to about 10 carbon atoms, and derivatives thereof. Non-limitingexamples of aliphatic dicarboxylic acids include malonic, malic,succinic, oxalic, glutaric, adipic, pimelic, azelaic, sebacic, fumaric,2,2-dimethyl glutaric, suberic, 1,3-cyclopentanedicarboxylic,1,4-cyclohexanedicarboxylic, 1,3-cyclohexanedicarboxylic, diglycolic,itaconic, maleic, and 2,5-norbornanedicarboxylic. Representativearomatic dicarboxylic acids that may be used include substituted andunsubstituted, linear or branched, aromatic dicarboxylic acids selectedfrom aromatic dicarboxylic acids containing 8 or more carbon atoms, andderivatives thereof. Non-limiting examples of aromatic dicarboxylicacids include terephthalic acid, dimethyl terephthalate, isophthalicacid, dimethyl isophthalate, 2,6-napthalene dicarboxylic acid,dimethyl-2,6-naphthalate, 2,7-naphthalenedicarboxylic acid,dimethyl-2,7-naphthalate, 3,4′-diphenyl ether dicarboxylic acid,dimethyl-3,4′diphenyl ether dicarboxylate, 4,4′-diphenyl etherdicarboxylic acid, dimethyl-4,4′-diphenyl ether dicarboxylate,3,4′-diphenyl sulfide dicarboxylic acid, dimethyl-3,4′-diphenyl sulfidedicarboxylate, 4,4′-diphenyl sulfide dicarboxylic acid,dimethyl-4,4′-diphenyl sulfide dicarboxylate, 3,4′-diphenyl sulfonedicarboxylic acid, dimethyl-3,4′-diphenyl sulfone dicarboxylate,4,4′-diphenyl sulfone dicarboxylic acid, dimethyl-4,4′-diphenyl sulfonedicarboxylate, 3,4′-benzophenonedicarboxylic acid,dimethyl-3,4′-benzophenonedicarboxylate, 4,4′-benzophenonedicarboxylicacid, dimethyl-4,4′-benzophenonedicarboxylate, 1,4-naphthalenedicarboxylic acid, dimethyl-1,4-naphthalate, 4,4′-methylene bis(benzoicacid), dimethyl-4,4% methylenebis(benzoate), etc., and mixtures thereof.

The polymerization may be catalyzed by a catalyst, such as atitanium-based catalyst (e.g., tetraisopropyltitanate, tetraisopropoxytitanium, dibutoxydiacetoacetoxy titanium, or tetrabutyltitanate). Ifdesired, a diisocyanate chain extender may be reacted with thecopolyester to increase its molecular weight. Representativediisocyanates may include toluene 2,4-diisocyanate, toluene2,6-diisocyanate, 2,4′-diphenylmethane diisocyanate,naphthylene-1,5-diisocyanate, xylylene diisocyanate, hexamethylenediisocyanate (“HMDI”), isophorone diisocyanate andmethylenebis(2-isocyanatocyclohexane). Trifunctional isocyanatecompounds may also be employed that contain isocyanurate and/or biureagroups with a functionality of not less than three, or to replace thediisocyanate compounds partially by tri-or polyisocyanates. Thepreferred diisocyanate is hexamethylene diisocyanate. The amount of thechain extender employed is typically from about 0.3 to about 3.5 wt. %,in some embodiments, from about 0.5 to about 2.5 wt. % based on thetotal weight percent of the polymer.

The copolyesters may either be a linear polymer or a long-chain branchedpolymer. Long-chain branched polymers are generally prepared by using alow molecular weight branching agent, such as a polyol, polycarboxylicacid, hydroxy acid, and so forth. Representative low molecular weightpolyols that may be employed as branching agents include glycerol,trimethylolpropane, trimethylolethane, polyethertriols,1,2,4-butanetriol, pentaerythritol, 1,2,6-hexanetriol, sorbitol,1,1,4,4,-tetrakis(hydroxymethyl)cyclohexane, tris(2-hydroxyethyl)isocyanurate, and dipentaerythritol. Representative higher molecularweight polyols (molecular weight of 400 to 3000) that may be used asbranching agents include triols derived by condensing alkylene oxideshaving 2 to 3 carbons, such as ethylene oxide and propylene oxide withpolyol initiators. Representative polycarboxylic acids that may be usedas branching agents include hemimellitic acid, trimellitic(1,2,4-benzenetricarboxylic) acid and anhydride, trimesic(1,3,5-benzenetricarboxylic) acid, pyromellitic acid and anhydride,benzenetetracarboxylic acid, benzophenone tetracarboxylic acid,1,1,2,2-ethane-tetracarboxylic acid, 1,1,2-ethanetricarboxylic acid,1,3,5-pentanetricarboxylic acid, and 1,2,3,4-cyclopentanetetracarboxylicacid. Representative hydroxy acids that may be used as branching agentsinclude malic acid, citric acid, tartaric acid, 3-hydroxyglutaric acid,mucic acid, trihydroxyglutaric acid, 4-carboxyphthalic anhydride,hydroxyisophthalic acid, and 4-(beta-hydroxyethyl)phthalic acid. Suchhydroxy acids contain a combination of 3 or more hydroxyl and carboxylgroups. Especially preferred branching agents include trimellitic acid,trimesic acid, pentaerythritol, trimethylol propane and1,2,4-butanetriol.

The aromatic dicarboxylic acid monomer constituent may be present in thecopolyester in an amount of from about 10 mole % to about 40 mole %, insome embodiments from about 15 mole % to about 35 mole %, and in someembodiments, from about 15 mole % to about 30 mole %. The aliphaticdicarboxylic acid monomer constituent may likewise be present in thecopolyester in an amount of from about 15 mole % to about 45 mole %, insome embodiments from about 20 mole % to about 40 mole %, and in someembodiments, from about 25 mole % to about 35 mole %. The polyol monomerconstituent may also be present in the aliphatic-aromatic copolyester inan amount of from about 30 mole % to about 65 mole %, in someembodiments from about 40 mole % to about 50 mole %, and in someembodiments, from about 45 mole % to about 55 mole %.

In one particular embodiment, for example, the aliphatic-aromaticcopolyester may comprise the following structure:

wherein,

m is an integer from 2 to 10, in some embodiments from 2 to 4, and inone embodiment, 4;

n is an integer from 0 to 18, in some embodiments from 2 to 4, and inone embodiment, 4;

p is an integer from 2 to 10, in some embodiments from 2 to 4, and inone embodiment, 4;

x is an integer greater than 1; and

y is an integer greater than 1. One example of such a copolyester ispolybutylene adipate terephthalate, which is commercially availableunder the designation ECOFLEX® F BX 7011 from BASF Corp. Another exampleof a suitable copolyester containing an aromatic terephtalic acidmonomer constituent is available under the designation ENPOL™ 8060M fromIRE Chemicals (South Korea). Other suitable aliphatic-aromaticcopolyesters may be described in U.S. Pat. Nos. 5,292,783; 5,446,079;5,559,171; 5,580,911; 5,599,858; 5,817,721; 5,900,322; and 6,258,924,which are incorporated herein in their entirety by reference thereto forall purposes.

B. Starch

A starch is also employed in the present invention that iswater-sensitive in that it contains one or more starches that aregenerally dispersible in water. Starch is a natural polymer composed ofamylose and amylopectin. Amylose is essentially a linear polymer havinga molecular weight in the range of 100,000-500,000, whereas amylopectinis a highly branched polymer having a molecular weight of up to severalmillion. Although starch is produced in many plants, typical sourcesincludes seeds of cereal grains, such as corn, waxy corn, wheat,sorghum, rice, and waxy rice; tubers, such as potatoes; roots, such astapioca (i.e., cassava and manioc), sweet potato, and arrowroot; and thepith of the sago palm. Broadly speaking, any natural (unmodified) and/ormodified starch having the desired water sensitivity properties may beemployed in the present invention. Modified starches, for instance, areoften employed that have been chemically modified by typical processesknown in the art (e.g., esterification, etherification, oxidation, acidhydrolysis, enzymatic hydrolysis, etc.). Starch ethers and/or esters maybe particularly desirable, such as hydroxyalkyl starches, carboxymethylstarches, etc. The hydroxyalkyl group of hydroxylalkyl starches maycontain, for instance, 2 to 10 carbon atoms, in some embodiments from 2to 6 carbon atoms, and in some embodiments, from 2 to 4 carbon atoms.Representative hydroxyalkyl starches such as hydroxyethyl starch,hydroxypropyl starch, hydroxybutyl starch, and derivatives thereof.Starch esters, for instance, may be prepared using a wide variety ofanhydrides (e.g., acetic, propionic, butyric, and so forth), organicacids, acid chlorides, or other esterification reagents. The degree ofesterification may vary as desired, such as from 1 to 3 ester groups perglucosidic unit of the starch.

C. Water-Soluble Polymer

The film also includes one or more water-soluble polymers. Withoutintending to be limited by theory, the present inventors believe thatsuch polymers may improve the compatibility between the starch andbiodegradable polyester, thereby leading to a film that exhibitsexcellent mechanical and physical properties during use. Such polymersmay be formed from monomers such as vinyl pyrrolidone, hydroxyethylacrylate or methacrylate (e.g., 2-hydroxyethyl methacrylate),hydroxypropyl acrylate or methacrylate, acrylic or methacrylic acid,acrylic or methacrylic esters or vinyl pyridine, acrylamide, vinylacetate, vinyl alcohol, ethylene oxide, derivatives thereof, and soforth. Other examples of suitable monomers are described in U.S. Pat.No. 4,499,154 to James, et al., which is incorporated herein in itsentirety by reference thereto for all purposes. The resulting polymersmay be homopolymers or interpolymers (e.g., copolymer, terpolymer,etc.), and may be nonionic, anionic, cationic, or amphoteric. Inaddition, the polymer may be of one type (i.e., homogeneous), ormixtures of different polymers may be used (i.e., heterogeneous).

In one particular embodiment, the water-soluble polymer contains arepeating unit having a functional hydroxyl group, such as polyvinylalcohol (“PVOH”), copolymers of polyvinyl alcohol (e.g., ethylene vinylalcohol copolymers, methyl methacrylate vinyl alcohol copolymers, etc.),etc. Vinyl alcohol polymers, for instance, have at least two or morevinyl alcohol units in the molecule and may be a homopolymer of vinylalcohol, or a copolymer containing other monomer units. Vinyl alcoholhomopolymers may be obtained by hydrolysis of a vinyl ester polymer,such as vinyl formate, vinyl acetate, vinyl propionate, etc. Vinylalcohol copolymers may be obtained by hydrolysis of a copolymer of avinyl ester with an olefin having 2 to 30 carbon atoms, such asethylene, propylene, 1-butene, etc.; an unsaturated carboxylic acidhaving 3 to 30 carbon atoms, such as acrylic acid, methacrylic acid,crotonic acid, maleic acid, fumaric acid, etc., or an ester, salt,anhydride or amide thereof; an unsaturated nitrile having 3 to 30 carbonatoms, such as acrylonitrile, methacrylonitrile, etc.; a vinyl etherhaving 3 to 30 carbon atoms, such as methyl vinyl ether, ethyl vinylether, etc.; and so forth. The degree of hydrolysis may be selected tooptimize solubility, etc., of the polymer. For example, the degree ofhydrolysis may be from about 60 mole % to about 95 mole %, in someembodiments from about 80 mole % to about 90 mole %, and in someembodiments, from about 85 mole % to about 89 mole %. Examples ofsuitable partially hydrolyzed polyvinyl alcohol polymers are availableunder the designation CELVOL™ 203, 205, 502, 504, 508, 513, 518, 523,530, or 540 from Celanese Corp. Other suitable partially hydrolyzedpolyvinyl alcohol polymers are available under the designation ELVANOL™50-14, 50-26, 50-42, 51-03, 51-04, 51-05, 51-08, and 52-22 from DuPont.

D. Plasticizer

A plasticizer is also employed in the film to help render thebiodegradable polyester, starch, and/or water-soluble polymermelt-processible. Starches, for instance, normally exist in the form ofgranules that have a coating or outer membrane that encapsulates themore water-soluble amylose and amylopectin chains within the interior ofthe granule. When heated, plasticizers (e.g., polar solvents) may softenand penetrate the outer membrane and cause the inner starch chains toabsorb water and swell. This swelling will, at some point, cause theouter shell to rupture and result in an irreversible destructurizationof the starch granule. Once destructurized, the starch polymer chainscontaining amylose and amylopectin polymers, which are initiallycompressed within the granules, will stretch out and form a generallydisordered intermingling of polymer chains. Upon resolidification,however, the chains may reorient themselves to form crystalline oramorphous solids having varying strengths depending on the orientationof the starch polymer chains. Because the starch (natural or modified)is thus capable of melting and resolidifying, it is generally considereda “thermoplastic starch.”

Suitable plasticizers may include, for instance, polyhydric alcoholplasticizers, such as sugars (e.g., glucose, sucrose, fructose,raffinose, maltodextrose, galactose, xylose, maltose, lactose, mannose,and erythrose), sugar alcohols (e.g., erythritol, xylitol, malitol,mannitol, and sorbitol), polyols (e.g., ethylene glycol, glycerol,propylene glycol, dipropylene glycol, butylene glycol, and hexanetriol), etc. Also suitable are hydrogen bond forming organic compoundswhich do not have hydroxyl group, including urea and urea derivatives;anhydrides of sugar alcohols such as sorbitan; animal proteins such asgelatin; vegetable proteins such as sunflower protein, soybean proteins,cotton seed proteins; and mixtures thereof. Other suitable plasticizersmay include phthalate esters, dimethyl and diethylsuccinate and relatedesters, glycerol triacetate, glycerol mono and diacetates, glycerolmono, di, and tripropionates, butanoates, stearates, lactic acid esters,citric acid esters, adipic acid esters, stearic acid esters, oleic acidesters, and other acid esters. Aliphatic acids may also be used, such asethylene acrylic acid, ethylene maleic acid, butadiene acrylic acid,butadiene maleic acid, propylene acrylic acid, propylene maleic acid,and other hydrocarbon based acids. A low molecular weight plasticizer ispreferred, such as less than about 20,000 g/mol, preferably less thanabout 5,000 g/mol and more preferably less than about 1,000 g/mol.

The plasticizer may be incorporated into the film using any of a varietyof known techniques. For example, the starch and/or water-solublepolymers may be “pre-plasticized” prior to incorporation into the film.Alternatively, one or more of the components may be plasticized at thesame time as they are blended together. Regardless, batch and/orcontinuous melt blending techniques may be employed to blend thecomponents. For example, a mixer/kneader, Banbury mixer, Farrelcontinuous mixer, single-screw extruder, twin-screw extruder, roll mill,etc., may be utilized. One particularly suitable melt-blending device isa co-rotating, twin-screw extruder (e.g., USALAB twin-screw extruderavailable from Thermo Electron Corporation of Stone, England or anextruder available from Werner-Pfreiderer from Ramsey, N.J.). Suchextruders may include feeding and venting ports and provide highintensity distributive and dispersive mixing. For example, a starchcomposition may be initially fed to a feeding port of the twin-screwextruder. Thereafter, a plasticizer may be injected into the starchcomposition. Alternatively, the starch composition may be simultaneouslyfed to the feed throat of the extruder or separately at a differentpoint along its length. Melt blending may occur at any of a variety oftemperatures, such as from about 30° C. to about 200° C., in someembodiments, from about 40° C. to about 160° C., and in someembodiments, from about 50° C. to about 150° C.

The amounts of the biodegradable polyester, starch, water-solublepolymer, and plasticizer employed in the film are controlled in thepresent invention to achieve a desirable balance betweenbiodegradability, mechanical strength, and water-sensitivity. Forexample, biodegradable polyesters typically constitute from about 1 wt.% to about 50 wt. %, in some embodiments from about 2 wt. % to about 40wt. %, and in some embodiments, from about 5 to about 35 wt. % of thefilm. Water-soluble polymers may constitute from about 0.1 wt. % toabout 40 wt. %, in some embodiments from about 1 wt. % to about 35 wt.%, and in some embodiments, from about 5 to about 30 wt. % of the film.Plasticizers may constitute from about 0.1 wt. % to about 40 wt. %, insome embodiments from about 1 wt. % to about 35 wt. %, and in someembodiments, from about 5 to about 30 wt. % of the film. Further,starches may constitute from about 0.5 wt. % to about 45 wt. %, in someembodiments from about 5 wt. % to about 35 wt. %, and in someembodiments, from about 10 to about 30 wt. % of the film. It should beunderstood that the weight of starch referenced herein includes anybound water that naturally occurs in the starch before mixing it withother components. Starches, for instance, typically have a bound watercontent of about 5% to 16% by weight of the starch.

E. Other Components

In addition to the components noted above, other additives may also beincorporated into the film of the present invention, such as dispersionaids, melt stabilizers, processing stabilizers, heat stabilizers, lightstabilizers, antioxidants, heat aging stabilizers, whitening agents,antiblocking agents, bonding agents, lubricants, fillers, etc.Dispersion aids, for instance, may also be employed to help create auniform dispersion of the starch/polyvinyl alcohol/plasticizer mixtureand retard or prevent separation into constituent phases. Likewise, thedispersion aids may also improve the water dispersibility of the film.When employed, the dispersion aid(s) typically constitute from about0.01 wt. % to about 15 wt. %, in some embodiments from about 0.1 wt. %to about 10 wt. %, and in some embodiments, from about 0.5 wt. % toabout 5 wt. % of the film. Although any dispersion aid may generally beemployed in the present invention, surfactants having a certainhydrophilic/lipophilic balance (“HLB”) may improve the long-termstability of the composition. The HLB index is well known in the art andis a scale that measures the balance between the hydrophilic andlipophilic solution tendencies of a compound. The HLB scale ranges from1 to approximately 50, with the lower numbers representing highlylipophilic tendencies and the higher numbers representing highlyhydrophilic tendencies. In some embodiments of the present invention,the HLB value of the surfactants is from about 1 to about 20, in someembodiments from about 1 to about 15 and in some embodiments, from about2 to about 10. If desired, two or more surfactants may be employed thathave HLB values either below or above the desired value, but togetherhave an average HLB value within the desired range.

One particularly suitable class of surfactants for use in the presentinvention are nonionic surfactants, which typically have a hydrophobicbase (e.g., long chain alkyl group or an alkylated aryl group) and ahydrophilic chain (e.g., chain containing ethoxy and/or propoxymoieties). For instance, some suitable nonionic surfactants that may beused include, but are not limited to, ethoxylated alkylphenols,ethoxylated and propoxylated fatty alcohols, polyethylene glycol ethersof methyl glucose, polyethylene glycol ethers of sorbitol, ethyleneoxide-propylene oxide block copolymers, ethoxylated esters of fatty(C₈-C₁₈) acids, condensation products of ethylene oxide with long chainamines or amides, condensation products of ethylene oxide with alcohols,fatty acid esters, monoglyceride or diglycerides of long chain alcohols,and mixtures thereof. In one particular embodiment, the nonionicsurfactant may be a fatty acid ester, such as a sucrose fatty acidester, glycerol fatty acid ester, propylene glycol fatty acid ester,sorbitan fatty acid ester, pentaerythritol fatty acid ester, sorbitolfatty acid ester, and so forth. The fatty acid used to form such estersmay be saturated or unsaturated, substituted or unsubstituted, and maycontain from 6 to 22 carbon atoms, in some embodiments from 8 to 18carbon atoms, and in some embodiments, from 12 to 14 carbon atoms. Inone particular embodiment, mono- and di-glycerides of fatty acids may beemployed in the present invention.

Fillers may also be employed in the present invention. Fillers areparticulates or other forms of material that may be added to the filmpolymer extrusion blend and that will not chemically interfere with theextruded film, but which may be uniformly dispersed throughout the film.Fillers may serve a variety of purposes, including enhancing filmopacity and/or breathability (i.e., vapor-permeable and substantiallyliquid-impermeable). For instance, filled films may be made breathableby stretching, which causes the polymer to break away from the fillerand create microporous passageways. Breathable microporous elastic filmsare described, for example, in U.S. Pat. Nos. 5,997,981; 6,015,764; and6,111,163 to McCormack, et al.; 5,932,497 to Morman, et al.; 6,461,457to Taylor, et al., which are incorporated herein in their entirety byreference thereto for all purposes. Further, hindered phenols arecommonly used as an antioxidant in the production of films. Somesuitable hindered phenols include those available from Ciba SpecialtyChemicals under the trade name “Irganox®”, such as Irganox® 1076, 1010,or E 201. Moreover, bonding agents may also be added to the film tofacilitate bonding of the film to additional materials (e.g., nonwovenwebs). Examples of such bonding agents include hydrogenated hydrocarbonresins. Other suitable bonding agents are described in U.S. Pat. Nos.4,789,699 to Kieffer et al. and 5,695,868 to McCormack, which areincorporated herein in their entirety by reference thereto for allpurposes.

II. Film Construction

The film of the present invention may be mono- or multi-layered.Multilayer films may be prepared by co-extrusion of the layers,extrusion coating, or by any conventional layering process. Suchmultilayer films normally contain at least one base layer and at leastone skin layer, but may contain any number of layers desired. Forexample, the multilayer film may be formed from a base layer and one ormore skin layers, wherein the base layer is formed from a blend of thebiodegradable polyester, starch, water-soluble polymer, and plasticizer.In most embodiments, the skin layer(s) are formed from a biodegradablepolyester, thermoplastic starch, water-soluble polymer, and plasticizeras described above. It should be understood, however, that otherpolymers may also be employed in the skin layer(s), such as polyolefinpolymers (e.g., linear low-density polyethylene (LLDPE) orpolypropylene). The term “linear low density polyethylene” refers topolymers of ethylene and higher alpha olefin comonomers, such as C₃-C₁₂and combinations thereof, having a Melt Index (as measured by ASTMD-1238) of from about 0.5 to about 30 grams per 10 minutes at 190° C.Examples of predominately linear polyolefin polymers include, withoutlimitation, polymers produced from the following monomers: ethylene,propylene, 1-butene, 4-methyl-pentene, 1-hexene, 1-octene and higherolefins as well as copolymers and terpolymers of the foregoing. Inaddition, copolymers of ethylene and other olefins including butene,4-methyl-pentene, hexene, heptene, octene, decene, etc., are alsoexamples of predominately linear polyolefin polymers. Additionalfilm-forming polymers that may be suitable for use with the presentinvention, alone or in combination with other polymers, include ethylenevinyl acetate, ethylene ethyl acrylate, ethylene acrylic acid, ethylenemethyl acrylate, ethylene normal butyl acrylate, nylon, ethylene vinylalcohol, polystyrene, polyurethane, and so forth.

Any known technique may be used to form a film from the compoundedmaterial, including blowing, casting, flat die extruding, etc. In oneparticular embodiment, the film may be formed by a blown process inwhich a gas (e.g., air) is used to expand a bubble of the extrudedpolymer blend through an annular die.

The bubble is then collapsed and collected in flat film form. Processesfor producing blown films are described, for instance, in U.S. Pat. Nos.3,354,506 to Raley; 3,650,649 to Schippers; and 3,801,429 to Schrenk etal., as well as U.S. Patent Application Publication Nos. 2005/0245162 toMcCormack, et al. and 2003/0068951 to Boggs, et al., all of which areincorporated herein in their entirety by reference thereto for allpurposes. In yet another embodiment, however, the film is formed using acasting technique.

Referring to FIG. 1, for instance, one embodiment of a method forforming a cast film is shown. The raw materials (e.g., biodegradablepolyester, starch, water-soluble polymer, plasticizer, etc.) may besupplied to a melt blending device, either separately or as a blend. Inone embodiment, for example, a starch, water-soluble polymer,plasticizer, and/or biodegradable polyester are separately supplied to amelt blending device where they are dispersively blended in a mannersuch as described above. For example, an extruder may be employed thatincludes feeding and venting ports. In one embodiment, the biodegradablepolyester may be fed to a feeding port of the twin-screw extruder andmelted. Thereafter, the starch, plasticizer, and water-soluble polymermay be fed into the polymer melt. Regardless, the materials are blendedunder high shear/pressure and heat to ensure sufficient mixing. Forexample, melt blending may occur at a temperature of from about 50° C.to about 300° C., in some embodiments, from about 70° C. to about 250°C., and in some embodiments, from about 90° C. to about 180° C.Likewise, the apparent shear rate during melt blending may range fromabout 100 seconds⁻¹ to about 10,000 seconds⁻¹, in some embodiments fromabout 500 seconds⁻¹ to about 5000 seconds⁻¹, and in some embodiments,from about 800 seconds⁻¹ to about 1200 seconds⁻¹. The apparent shearrate is equal to 4Q/πR³, where Q is the volumetric flow rate (“m³/s”) ofthe polymer melt and R is the radius (“m”) of the capillary (e.g.,extruder die) through which the melted polymer flows.

Thereafter, the extruded material may be immediately chilled and cutinto pellet form. In the particular embodiment of FIG. 1, the compoundedmaterial (not shown) is then supplied to an extrusion apparatus 80 andcast onto a casting roll 90 to form a single-layered precursor film 10a. If a multilayered film is to be produced, the multiple layers areco-extruded together onto the casting roll 90. The casting roll 90 mayoptionally be provided with embossing elements to impart a pattern tothe film. Typically, the casting roll 90 is kept at temperaturesufficient to solidify and quench the sheet 10 a as it is formed, suchas from about 20 to 60° C. If desired, a vacuum box may be positionedadjacent to the casting roll 90 to help keep the precursor film 10 aclose to the surface of the roll 90. Additionally, air knives orelectrostatic pinners may help force the precursor film 10 a against thesurface of the casting roll 90 as it moves around a spinning roll. Anair knife is a device known in the art that focuses a stream of air at avery high flow rate to pin the edges of the film.

Once cast, the film 10 a may then be optionally oriented in one or moredirections to further improve film uniformity and reduce thickness.Orientation may also form micropores in a film containing a filler, thusproviding breathability to the film. For example, the film may beimmediately reheated to a temperature below the melting point of one ormore polymers in the film, but high enough to enable the composition tobe drawn or stretched. In the case of sequential orientation, the“softened” film is drawn by rolls rotating at different speeds ofrotation such that the sheet is stretched to the desired draw ratio inthe longitudinal direction (machine direction). This “uniaxially”oriented film may then be laminated to a fibrous web. In addition, theuniaxially oriented film may also be oriented in the cross-machinedirection to form a “biaxially oriented” film. For example, the film maybe clamped at its lateral edges by chain clips and conveyed into atenter oven. In the tenter oven, the film may be reheated and drawn inthe cross-machine direction to the desired draw ratio by chain clipsdiverged in their forward travel.

Referring again to FIG. 1, for instance, one method for forming auniaxially oriented film is shown. As illustrated, the precursor film 10a is directed to a film-orientation unit 100 or machine directionorienter (“MDO”), such as commercially available from Marshall andWillams, Co. of Providence, R.I. The MDO has a plurality of stretchingrolls (such as from 5 to 8) which progressively stretch and thin thefilm in the machine direction, which is the direction of travel of thefilm through the process as shown in FIG. 1. While the MDO 100 isillustrated with eight rolls, it should be understood that the number ofrolls may be higher or lower, depending on the level of stretch that isdesired and the degrees of stretching between each roll. The film may bestretched in either single or multiple discrete stretching operations.It should be noted that some of the rolls in an MDO apparatus may not beoperating at progressively higher speeds. If desired, some of the rollsof the MDO 100 may act as preheat rolls. If present, these first fewrolls heat the film 10 a above room temperature (e.g., to 125° F.). Theprogressively faster speeds of adjacent rolls in the MDO act to stretchthe film 10 a. The rate at which the stretch rolls rotate determines theamount of stretch in the film and final film weight.

The resulting film 10 b may then be wound and stored on a take-up roll60. While not shown here, various additional potential processing and/orfinishing steps known in the art, such as slitting, treating,aperturing, printing graphics, or lamination of the film with otherlayers (e.g., nonwoven web materials), may be performed withoutdeparting from the spirit and scope of the invention.

The thickness of the resulting water-sensitive biodegradable film maygenerally vary depending upon the desired use. Nevertheless, the filmthickness is typically minimized to reduce the time needed for the filmto disperse in water. Thus, in most embodiments of the presentinvention, the water-sensitive biodegradable film has a thickness ofabout 50 micrometers or less, in some embodiments from about 1 to about40 micrometers, in some embodiments from about 2 to about 35micrometers, and in some embodiments, from about 5 to about 30micrometers.

Despite having such a small thickness and good sensitivity in water, thefilm of the present invention is nevertheless able to retain good drymechanical properties during use. One parameter that is indicative ofthe relative dry strength of the film is the ultimate tensile strength,which is equal to the peak stress obtained in a stress-strain curve.Desirably, the film of the present invention exhibits an ultimatetensile strength in the machine direction (“MD”) of from about 10 toabout 80 Megapascals (MPa), in some embodiments from about 15 to about60 MPa, and in some embodiments, from about 20 to about 50 MPa, and anultimate tensile strength in the cross-machine direction (“CD”) of fromabout 2 to about 40 Megapascals (MPa), in some embodiments from about 4to about 40 MPa, and in some embodiments, from about 5 to about 30 MPa.Although possessing good strength, it is also desirable that the film isnot too stiff. One parameter that is indicative of the relativestiffness of the film (when dry) is Young's modulus of elasticity, whichis equal to the ratio of the tensile stress to the tensile strain and isdetermined from the slope of a stress-strain curve. For example, thefilm typically exhibits a Young's modulus in the machine direction(“MD”) of from about 50 to about 1200 Megapascals (“MPa”), in someembodiments from about 200 to about 1000 MPa, and in some embodiments,from about 400 to about 800 MPa, and a Young's modulus in thecross-machine direction (“CD”) of from about 50 to about 1000Megapascals (“MPa”), in some embodiments from about 100 to about 800MPa, and in some embodiments, from about 150 to about 500 MPa. The MDand CD elongation of the film may also be about 50% or more, in someembodiments about 100% or more, and in some embodiments, about 150% ormore.

The water-sensitive biodegradable film of the present invention may beused in a wide variety of applications. For example, as indicated above,the film may be used in an absorbent article. An “absorbent article”generally refers to any article capable of absorbing water or otherfluids. Examples of some absorbent articles include, but are not limitedto, personal care absorbent articles, such as diapers, training pants,absorbent underpants, incontinence articles, feminine hygiene products(e.g., sanitary napkins, pantiliners, etc.), swim wear, baby wipes, andso forth; medical absorbent articles, such as garments, fenestrationmaterials, underpads, bedpads, bandages, absorbent drapes, and medicalwipes; food service wipers; clothing articles; and so forth. Severalexamples of such absorbent articles are described in U.S. Pat. Nos.5,649,916 to DiPalma, et al.; 6,110,158 to Kielpikowski; 6,663,611 toBlaney, et al., which are incorporated herein in their entirety byreference thereto for all purposes. Still other suitable articles aredescribed in U.S. Patent Application Publication No. 2004/0060112 A1 toFell et al., as well as U.S. Pat. Nos. 4,886,512 to Damico et al.;5,558,659 to Sherrod et al.; 6,888,044 to Fell et al.; and 6,511,465 toFreiburger et al., all of which are incorporated herein in theirentirety by reference thereto for all purposes. Materials and processessuitable for forming such absorbent articles are well known to thoseskilled in the art.

As is well known in the art, the absorbent article may be provided withadhesives (e.g., pressure-sensitive adhesives) that help removablysecure the article to the crotch portion of an undergarment and/or wrapup the article for disposal. Suitable pressure-sensitive adhesives, forinstance, may include acrylic adhesives, natural rubber adhesives,tackified block copolymer adhesives, polyvinyl acetate adhesives,ethylene vinyl acetate adhesives, silicone adhesives, polyurethaneadhesives, thermosettable pressure-sensitive adhesives, such as epoxyacrylate or epoxy polyester pressure-sensitive adhesives, etc. Suchpressure-sensitive adhesives are known in the art and are described inthe Handbook of Pressure Sensitive Adhesive Technology, Satas (Donatas),1989, 2^(nd) edition, Van Nostrand Reinhold. The pressure sensitiveadhesives may also include additives such as cross-linking agents,fillers, gases, blowing agents, glass or polymeric microspheres, silica,calcium carbonate fibers, surfactants, and so forth. The additives areincluded in amounts sufficient to affect the desired properties.

The location of the adhesive on the absorbent article is not criticaland may vary widely depending on the intended use of the article. Forexample, certain feminine hygiene products (e.g., sanitary napkins) mayhave wings or flaps that laterally from a central absorbent core and areintended to be folded around the edges of the wearer's panties in thecrotch region. The flaps may be provided with an adhesive (e.g.,pressure-sensitive adhesive) for affixing the flaps to the underside ofthe wearer's panties.

Regardless of the particular location of the adhesive, however, arelease liner may be employed to cover the adhesive, thereby protectingit from dirt, drying out, and premature sticking prior to use. Therelease liner may contain a release coating that enhances the ability ofthe liner to be peeled from an adhesive. The release coating contains arelease agent, such as a hydrophobic polymer.

Exemplary hydrophobic polymers include, for instance, silicones (e.g.,polysiloxanes, epoxy silicones, etc.), perfluoroethers, fluorocarbons,polyurethanes, and so forth. Examples of such release agents aredescribed, for instance, in U.S. Pat. Nos. 6,530,910 to Pomplun, et al.;5,985,396 to Kerins, et al.; and 5,981,012 to Pomplun, et al., which areincorporated herein in their entirety by reference thereto for allpurposes. One particularly suitable release agent is an amorphouspolyolefin having a melt viscosity of about 400 to about 10,000 cps at190° C., such as made by the U.S. Rexene Company under the tradenameREXTAC® (e.g., RT2315, RT2535 and RT2330). The release coating may alsocontain a detackifier, such as a low molecular weight, highly branchedpolyolefin. A particularly suitable low molecular weight, highlybranched polyolefin is VYBAR® 253, which is made by the PetroliteCorporation. Other additives may also be employed in the releasecoating, such as compatibilizers, processing aids, plasticizers,tackifiers, slip agents, and antimicrobial agents, and so forth. Therelease coating may be applied to one or both surfaces of the liner, andmay cover all or only a portion of a surface. Any suitable technique maybe employed to apply the release coating, such as solvent-based coating,hot melt coating, solventless coating, etc. Solvent-based coatings aretypically applied to the release liner by processes such as rollcoating, knife coating, curtain coating, gravure coating, wound rodcoating, and so forth. The solvent (e.g., water) is then removed bydrying in an oven, and the coating is optionally cured in the oven.Solventless coatings may include solid compositions, such as siliconesor epoxy silicones, which are coated onto the liner and then cured byexposure to ultraviolet light. Optional steps include priming the linerbefore coating or surface modification of the liner, such as with coronatreatment. Hot melt coatings, such as polyethylenes or perfluoroethers,may be heated and then applied through a die or with a heated knife. Hotmelt coatings may be applied by co-extruding the release agent with therelease liner in blown film or sheet extruder for ease of coating andfor process efficiency.

To facilitate its ability to be easily disposed, the release liner maybe formed from a water-sensitive biodegradable film in accordance withthe present invention. In this regard, one particular embodiment of asanitary napkin that may employ the water-sensitive biodegradable filmof the present invention will now be described in more detail. Forpurposes of illustration only, an absorbent article 20 is shown in FIG.2 as a sanitary napkin for feminine hygiene. In the illustratedembodiment, the absorbent article 20 includes a main body portion 22containing a topsheet 40, an outer cover or backsheet 42, an absorbentcore 44 positioned between the backsheet 42 and the topsheet 40, and apair of flaps 24 extending from each longitudinal side 22 a of the mainbody portion 22. The topsheet 40 defines a bodyfacing surface of theabsorbent article 20. The absorbent core 44 is positioned inward fromthe outer periphery of the absorbent article 20 and includes abody-facing side positioned adjacent the topsheet 40 and agarment-facing surface positioned adjacent the backsheet 42.

The topsheet 40 is generally designed to contact the body of the userand is liquid-permeable. The topsheet 40 may surround the absorbent core44 so that it completely encases the absorbent article 20.Alternatively, the topsheet 40 and the backsheet 42 may extend beyondthe absorbent core 44 and be peripherally joined together, eitherentirely or partially, using known techniques. Typically, the topsheet40 and the backsheet 42 are joined by adhesive bonding, ultrasonicbonding, or any other suitable joining method known in the art. Thetopsheet 40 is sanitary, clean in appearance, and somewhat opaque tohide bodily discharges collected in and absorbed by the absorbent core44. The topsheet 40 further exhibits good strike-through and rewetcharacteristics permitting bodily discharges to rapidly penetratethrough the topsheet 40 to the absorbent core 44, but not allow the bodyfluid to flow back through the topsheet 40 to the skin of the wearer.For example, some suitable materials that may be used for the topsheet40 include nonwoven materials, perforated thermoplastic films, orcombinations thereof. A nonwoven fabric made from polyester,polyethylene, polypropylene, bicomponent, nylon, rayon, or like fibersmay be utilized. For instance, a white uniform spunbond material isparticularly desirable because the color exhibits good maskingproperties to hide menses that has passed through it. U.S. Pat. No.4,801,494 to Datta, et al. and U.S. Pat. No. 4,908,026 to Sukiennik, etal. teach various other cover materials that may be used in the presentinvention.

The topsheet 40 may also contain a plurality of apertures (not shown)formed therethrough to permit body fluid to pass more readily into theabsorbent core 44. The apertures may be randomly or uniformly arrangedthroughout the topsheet 40, or they may be located only in the narrowlongitudinal band or strip arranged along the longitudinal axis X-X ofthe absorbent article 20. The apertures permit rapid penetration of bodyfluid down into the absorbent core 44. The size, shape, diameter andnumber of apertures may be varied to suit one's particular needs.

As stated above, the absorbent article also includes a backsheet 42. Thebacksheet 42 is generally liquid-impermeable and designed to face theinner surface, i.e., the crotch portion of an undergarment (not shown).The backsheet 42 may permit a passage of air or vapor out of theabsorbent article 20, while still blocking the passage of liquids. Anyliquid-impermeable material may generally be utilized to form thebacksheet 42. For example, one suitable material that may be utilized isa microembossed polymeric film, such as polyethylene or polypropylene.In particular embodiments, a polyethylene film is utilized that has athickness in the range of about 0.2 mils to about 5.0 mils, andparticularly between about 0.5 to about 3.0 mils.

The absorbent article 20 also contains an absorbent core 44 positionedbetween the topsheet 40 and the backsheet 42. The absorbent core 44 maybe formed from a single absorbent member or a composite containingseparate and distinct absorbent members. It should be understood,however, that any number of absorbent members may be utilized in thepresent invention. For example, in one embodiment, the absorbent core 44may contain an intake member (not shown) positioned between the topsheet40 and a transfer delay member (not shown). The intake member may bemade of a material that is capable of rapidly transferring, in thez-direction, body fluid that is delivered to the topsheet 40. The intakemember may generally have any shape and/or size desired. In oneembodiment, the intake member has a rectangular shape, with a lengthequal to or less than the overall length of the absorbent article 20,and a width less than the width of the absorbent article 20. Forexample, a length of between about 150 mm to about 300 mm and a width ofbetween about 10 mm to about 60 mm may be utilized.

Any of a variety of different materials may be used for the intakemember to accomplish the above-mentioned functions. The material may besynthetic, cellulosic, or a combination of synthetic and cellulosicmaterials. For example, airlaid cellulosic tissues may be suitable foruse in the intake member. The airlaid cellulosic tissue may have a basisweight ranging from about 10 grams per square meter (gsm) to about 300gsm, and in some embodiments, between about 100 gsm to about 250 gsm. Inone embodiment, the airlaid cellulosic tissue has a basis weight ofabout 200 gsm. The airlaid tissue may be formed from hardwood and/orsoftwood fibers. The airlaid tissue has a fine pore structure andprovides an excellent wicking capacity, especially for menses.

If desired, a transfer delay member (not shown) may be positionedvertically below the intake member. The transfer delay member maycontain a material that is less hydrophilic than the other absorbentmembers, and may generally be characterized as being substantiallyhydrophobic. For example, the transfer delay member may be a nonwovenfibrous web composed of a relatively hydrophobic material, such aspolypropylene, polyethylene, polyester or the like, and also may becomposed of a blend of such materials. One example of a materialsuitable for the transfer delay member is a spunbond web composed ofpolypropylene, multi-lobal fibers. Further examples of suitable transferdelay member materials include spunbond webs composed of polypropylenefibers, which may be round, tri-lobal or poly-lobal in cross-sectionalshape and which may be hollow or solid in structure. Typically the websare bonded, such as by thermal bonding, over about 3% to about 30% ofthe web area. Other examples of suitable materials that may be used forthe transfer delay member are described in U.S. Pat. No. 4,798,603 toMeyer, et al. and U.S. Pat. No. 5,248,309 to Serbiak, et al., which areincorporated herein in their entirety by reference thereto for allpurposes. To adjust the performance of the invention, the transfer delaymember may also be treated with a selected amount of surfactant toincrease its initial wettability.

The transfer delay member may generally have any size, such as a lengthof about 150 mm to about 300 mm. Typically, the length of the transferdelay member is approximately equal to the length of the absorbentarticle 20. The transfer delay member may also be equal in width to theintake member, but is typically wider. For example, the width of thetransfer delay member may be from between about 50 mm to about 75 mm,and particularly about 48 mm. The transfer delay member typically has abasis weight less than that of the other absorbent members. For example,the basis weight of the transfer delay member is typically less thanabout 150 grams per square meter (gsm), and in some embodiments, betweenabout 10 gsm to about 100 gsm. In one particular embodiment, thetransfer delay member is formed from a spunbonded web having a basisweight of about 30 gsm.

Besides the above-mentioned members, the absorbent core 44 may alsoinclude a composite absorbent member (not shown), such as a coformmaterial. In this instance, fluids may be wicked from the transfer delaymember into the composite absorbent member. The composite absorbentmember may be formed separately from the intake member and/or transferdelay member, or may be formed simultaneously therewith. In oneembodiment, for example, the composite absorbent member may be formed onthe transfer delay member or intake member, which acts a carrier duringthe coform process described above.

Regardless of its particular construction, the absorbent article 20typically contains an adhesive for securing to an undergarment. Anadhesive may be provided at any location of the absorbent article 20,such as on the lower surface of the backsheet 42. In this particularembodiment, the backsheet 42 carries a longitudinally central strip ofgarment adhesive 54 covered before use by a peelable release liner 58,which may be formed in accordance with the present invention. Each ofthe flaps 24 may also contain an adhesive 56 positioned adjacent to thedistal edge 34 of the flap 24. A peelable release liner 57, which mayalso be formed in accordance with the present invention, may cover theadhesive 56 before use. Thus, when a user of the sanitary absorbentarticle 20 wishes to expose the adhesives 54 and 56 and secure theabsorbent article 20 to the underside of an undergarment, the usersimply peels away the liners 57 and 58 and disposed them in awater-based disposal system (e.g., in a toilet).

Although various configurations of a release liner have been describedabove, it should be understood that other release liner configurationsare also included within the scope of the present invention. Further,the present invention is by no means limited to release liners and thewater-sensitive biodegradable film may be incorporated into a variety ofdifferent components of an absorbent article. For example, referringagain to FIG. 2, the backsheet 42 of the napkin 20 may include thewater-sensitive film of the present invention. In such embodiments, thefilm may be used alone to form the backsheet 42 or laminated to one ormore additional materials, such as a nonwoven web. The water-sensitivebiodegradable film of the present invention may also be used inapplications other than absorbent articles. For example, the film may beemployed as an individual wrap, packaging pouch, or bag for the disposalof a variety of articles, such as food products, absorbent articles,etc. Various suitable pouch, wrap, or bag configurations for absorbentarticles are disclosed, for instance, in U.S. Pat. Nos. 6,716,203 toSorebo, et al. and 6,380,445 to Moder, et al., as well as U.S. PatentApplication Publication No. 2003/0116462 to Sorebo, et al., all of whichare incorporated herein in their entirety by reference thereto for allpurposes.

The present invention may be better understood with reference to thefollowing examples.

Test Methods

Tensile Properties:

The strip tensile strength values were determined in substantialaccordance with ASTM Standard D-5034. A constant-rate-of-extension typeof tensile tester was employed. The tensile testing system was a Sintech1/D tensile tester, which is available from Sintech Corp. of Cary, N.C.The tensile tester was equipped with TESTWORKS 4.08B software from MTSCorporation to support the testing. An appropriate load cell wasselected so that the tested value fell within the range of 10-90% of thefull scale load. The film samples were initially cut into dog-boneshapes with a center width of 3.0 mm before testing. The samples wereheld between grips having a front and back face measuring 25.4millimeters×76 millimeters. The grip faces were rubberized, and thelonger dimension of the grip was perpendicular to the direction of pull.The grip pressure was pneumatically maintained at a pressure of 40pounds per square inch. The tensile test was run using a gauge length of18.0 millimeters and a break sensitivity of 40%. Five samples weretested by applying the test load along the machine-direction and fivesamples were tested by applying the test load along the cross direction.During the test, samples were stretched at a crosshead speed of abut 127millimeters per minute until breakage occurred. The modulus, peakstress, peak strain (i.e., % strain at peak load), and elongation weremeasured.

Water Disintegration Test:

The rate of film disintegration in tap water was tested using a “sloshbox”, which has a physical dimension of a 14″×18″×12″ high plastic boxon a hinged platform. One end of the platform is attached to thereciprocating cam. The typical amplitude is ±2″ (4″ range), withsloshing occurring at 0.5˜1.5 sloshes per second. The preferred actionis 0.9˜1.3 sloshes per second. During a test, the slosh box rocks up anddown with the water inside, “sloshing” back and forth. This actionproduces a wave front and intermittent motion on a sample susceptible todispersing in water. To quantify a measurement of sample filmdisintegration in water, without image analysis, simply timing issufficient. Three liters of tap water were added into the slosh box andresulted in ˜5.5″ water depth in the box. A frequency of 3.5 wasselected for the testing. Each film sample was cut into 1″×3″ size.Three pieces were dropped into the slosh box. The time to disintegratethe sample under the defined conditions was recorded twice for eachsample. The average of the time to the sample disintegration is thenreported. Generally, films reach an acceptable dispersion point when nopiece is larger than 25 mm² in size within 6 hours of agitation.

Example 1

A thermoplastic hydroxypropylated starch was formed as follows.Initially, a mixture of a hydroxypropylated starch (Glucosol 800,manufactured by Chemstar Products Company, Minneapolis, Minn.),surfactant (Excel P-40S, Kao Corporation, Tokyo, Japan), and plasticizer(sorbitol) was made at a ratio of the 66 parts of starch, 4 parts ofsurfactant, and 30 parts of plasticizer. A Hobart mixer was used formixing. The mixture was then added to a K-Tron feeder (K-Tron America,Pitman, N.J.) that fed the material into a co-rotating, twin-screwextruder (ZSK-30, diameter of 30 mm) that was manufactured by Werner andPfleiderer Corporation of Ramsey, N.J. The screw length was 1328millimeters. The extruder had 14 barrels, numbered consecutively 1-14from the feed hopper to the die. The first barrel #1 received themixture at 19 lbs/hr when the extruder was heated to a temperature forzones 1 to 7 of 100° C., 110° C., 124° C., 124° C., 124° C., 110° C.,and 105° C., respectively. The screw speed was set at 160 rpm to achievea melt pressure of 400-500 psi and a torque of 50-60%. In some cases, avent was also opened to release steam generated due to the presence ofthe added water in the plasticizer and inherent moisture in the starch.The strands cooled down through a cooling belt (Minarik ElectricCompany, Glendale, Calif.). A pelletizer (Conair, Bay City, Mich.) wasused to cut the strands to produce thermoplastic starch pellets, whichwere then collected and sealed in a bag.

Example 2

A plasticized polyvinyl alcohol was formed as follows. Initially, amixture of a polyvinyl alcohol (Elvanol 51-05, a granular polymer havinga degree of hydrolysis of 87.0-89.0 mole % and manufactured by DuPont)and plasticizer (sorbitol) was made at a ratio of the 80 parts polyvinylalcohol and 20 parts of plasticizer. A Hobart mixer was used for mixing.The mixture was then added to a K-Tron feeder (K-Tron America, Pitman,N.J.) that fed the material into a ZSK-30 co-rotating, twin-screwextruder as described above. The first barrel #1 received the mixture at25 lbs/hr when the extruder was heated to a temperature for zones 1 to 7of 150° C., 160° C., 185° C., 190° C., 190° C., 170° C., and 110° C.,respectively. The screw speed was set at 160 rpm to achieve a meltpressure of 280-300 psi and a torque of 34-40%. In some cases, a ventwas also opened release steam generated due to the presence of the addedwater in the plasticizer and inherent moisture in the starch. Thestrands cooled down through a cooling belt (Minarik Electric Company,Glendale, Calif.). A pelletizer (Conair, Bay City, Mich.) was used tocut the strands to produce polyvinyl alcohol pellets, which were thencollected and sealed in a bag.

Example 3

A plasticized polyvinyl alcohol was formed as follows. Initially, amixture of a polyvinyl alcohol (Celvol 203, a polymer having a degree ofhydrolysis of 87.0-89.0 mole % and manufactured by Celanese Chemicals)and plasticizer (sorbitol) was made at a ratio of the 80 parts polyvinylalcohol and 20 parts of plasticizer. A Hobart mixer was used for mixing.The mixture was then added to a K-Tron feeder (K-Trop America, Pitman,N.J.) that fed the material into a ZSK-30 co-rotating, twin-screwextruder as described above. The first barrel #1 received the mixture at25 lbs/hr when the extruder was heated to a temperature for zones 1 to 7of 150° C., 160° C., 185° C., 190° C., 190° C., 170° C., and 110° C.,respectively. The screw speed was set at 160 rpm to achieve a meltpressure of 280-300 psi and a torque of 34-40%. In some cases, a ventwas also opened release steam generated due to the presence of the addedwater in the plasticizer and inherent moisture in the starch. Thestrands cooled down through a cooling belt (Minarik Electric Company,Glendale, Calif.). A pelletizer (Conair, Bay City, Mich.) was used tocut the strands to produce polyvinyl alcohol pellets, which were thencollected and sealed in a bag.

Example 4

A blend of hydroxypropylated starch and polyvinyl alcohol was formed asfollows. Initially, a mixture of a hydroxypropylated starch (Glucosol800), surfactant (Excel P-40S), plasticizer (sorbitol), and polyvinylalcohol (Elvanol 51-05) was made at a ratio of the 36 parts of starch,30 parts polyvinyl alcohol, 4 parts of surfactant, and 30 parts ofplasticizer. A Hobart mixer was used for mixing. The mixture was thenadded to a K-Tron feeder (K-Tron America, Pitman, N.J.) that fed thematerial into a ZSK-30 co-rotating, twin-screw extruder as describedabove. The first barrel #1 received the mixture at 20 lbs/hr when theextruder was heated to a temperature for zones 1 to 7 of 95° C., 125°C., 140° C., 150° C., 150° C., 145° C., and 130° C., respectively. Thescrew speed was set at 150-160 rpm to achieve a melt pressure of 530-550psi and a torque of 80-90%. In some cases, a vent was also openedrelease steam generated due to the presence of the added water in theplasticizer and inherent moisture in the starch. The strands cooled downthrough a cooling belt (Minarik Electric Company, Glendale, Calif.). Apelletizer (Conair, Bay City, Mich.) was used to cut the strands toproduce pellets, which were then collected and sealed in a bag.

Example 5

A blend of starch and polyvinyl alcohol was formed as follows.Initially, a mixture of native corn starch (Cargill, Minneapolis,Minn.), surfactant (Excel P-40S), plasticizer (sorbitol), and polyvinylalcohol (Elvanol 51-05) was made at a ratio of the 38 parts of starch,30 parts polyvinyl alcohol, 2 parts of surfactant, and 30 parts ofplasticizer. A Hobart mixer was used for mixing. The mixture was thenadded to a K-Tron feeder (K-Tron America, Pitman, N.J.) that fed thematerial into a ZSK-30 co-rotating, twin-screw extruder as describedabove. The first barrel #1 received the mixture at 20 lbs/hr when theextruder was heated to a temperature for zones 1 to 7 of 95° C., 125°C., 140° C., 150° C., 150° C., 145° C., and 130° C., respectively. Thescrew speed was set at 150-160 rpm to achieve a melt pressure of 530-550psi and a torque of 80-90%. In some cases, a vent was also openedrelease steam generated due to the presence of the added water in theplasticizer and inherent moisture in the starch. The strands cooled downthrough a cooling belt (Minarik Electric Company, Glendale, Calif.). Apelletizer (Conair, Bay City, Mich.) was used to cut the strands toproduce pellets, which were then collected and sealed in a bag.

Example 6

A blend of hydroxypropylated starch and polyvinyl alcohol was formed asfollows. Initially, a mixture of a hydroxypropylated starch (Glucosol800), surfactant (Excel P-40S), plasticizer (sorbitol), and polyvinylalcohol (Celvol 203) was made at a ratio of the 36 parts of starch, 30parts polyvinyl alcohol, 4 parts of surfactant, and 30 parts ofplasticizer. A Hobart mixer was used for mixing. The mixture was thenadded to a K-Tron feeder (K-Tron America, Pitman, N.J.) that fed thematerial into a ZSK-30 co-rotating, twin-screw extruder as describedabove. The first barrel #1 received the mixture at 10 lbs/hr when theextruder was heated to a temperature for zones 1 to 7 of 95° C., 125°C., 140° C., 150° C., 150° C., 145° C., and 130° C., respectively. Thescrew speed was set at 150-160 rpm to achieve a melt pressure of 530-550psi and a torque of 80-90%. In some cases, a vent was also openedrelease steam generated due to the presence of the added water in theplasticizer and inherent moisture in the starch. The strands cooled downthrough a cooling belt (Minarik Electric Company, Glendale, Calif.). Apelletizer (Conair, Bay City, Mich.) was used to cut the strands toproduce pellets, which were then collected and sealed in a bag.

Examples 7-9

Various combinations of the starch of Example 1 and the polyvinylalcohol of Examples 2-3 were compounded with an Ecoflex® F BX 7011 resin(BASF, Florham Park, N.J.) using the ZSK-30 twin screw extruderdescribed above. The strands from the die was pelletized. The extrusionconditions are set forth below in Tables 1-2:

TABLE 1 Composition of Film Resin Feeding Starch of Ex. 1 PVA of Ex. 2Ecoflex ® Sample Rate (lb/hr) (wt. %) (wt. %) (wt. %) 7 20 60 30 10 8 2070 20 10 9 20 70 30 0

TABLE 2 Extrusion Conditions Extruder Speed Extruder Temperature Profile(° C.) P_(melt) Torque Sample (rpm) T₁ T₂ T₃ T₄ T₅ T₆ T₇ T_(melt) (psi)(%) 7 160 100 140 160 160 160 155 140 155 250-300 65-75 8 160 100 140160 160 160 155 140 155 250-300 65-75 9 160 100 140 160 160 160 155 140155 250-300 65-75

Examples 10-12

Glucosol 800 starch, Elvanol 51-05, sorbitol, and surfactant (ExcelP-40S) were initially mixed in a Hobart mixer at 36%, 30%, 30%, and 4%,respectively. The mixture was fed into ZSK-30 using K-Tron feeder.Separately, Ecoflex® F BX 7011 resin (BASF, Florham Park, N.J.) was fedfrom another K-Tron feeder into ZSK-30 for single-step compounding. Thisprocess reduces the thermal degradation of materials during blendpreparation. The strands from the die were pelletized. The extrusionconditions are set forth below in Table 3 and 4.

TABLE 3 Composition of Film Mixture of Glucosol 800, Elvanol 51-05,sorbitol, Resin Feeding and Excel P-40S Ecoflex ® Sample Rate (lb/hr)(wt. %) (wt. %) 10 20 90 10 11 20 80 20 12 20 70 30

TABLE 4 Extrusion Conditions Extruder Speed Extruder Temperature Profile(° C.) P_(melt) Torque Sample (rpm) T₁ T₂ T₃ T₄ T₅ T₆ T₇ T_(melt) (psi)(%) 10 160 100 124 150 150 150 145 130 144 290-310 80-90 11 160 100 124150 150 150 145 130 144 290-310 80-90 12 160 100 124 150 150 150 145 130144 290-310 80-90

Examples 13-15

Plasticized hydroxypropylated starch from Example 1, plasticizedpolyvinyl alcohol (Aqua-Sol™ 116, which is available from A. Schulman,Inc.), and Ecoflex®F BX 7011 resin (BASF, Florham Park, N.J.) werecompounded at varying ratios using the ZSK-30 twin screw extruderdescribed above. The strands from the die were pelletized. The extrusionconditions are set forth below in Table 5.

TABLE 5 Extrusion Conditions Resin Extruder Feeding Rate TPS AquasolEcoflex Speed Extruder Temperature Profile (° C.) P_(melt) Torque SampleNo. (lb/hr) (%) (%) (%) (rpm) T₁ T₂ T₃ T₄ T₅ T₆ T₇ T_(melt) (psi) (%)Example 13 30 70 30 0 150 100 135 170 170 165 150 150 162 250-300 70-79Example 14 30 60 30 10 150 100 135 170 170 165 150 150 162 250-300 70-79Example 15 30 70 20 10 150 100 135 170 170 165 150 150 162 250~300 70~79

Example 16

Blown films were formed from the blends of Examples 1-3 and 7-15 A HAAKETW-100 Twin Screw Extruder was employed using the conditions provided inTable 6.

TABLE 6 Processing Conditions for Making Blown Films TW-100 Twin ScrewExtruder Screw Speed: 40~50 rpm Die gap: 20 mil Zone 1: 170° C.Temperature Zone 2: 180° C. Zone 3: 190° C. Zone 4 (pump): 180° C. Zone5 (die): 170° C. Melt temperature: ~175° C. Film thickness: ~1.0 mil

Once formed, the films were subjected to the above-described tensile andwater disintegration tests. The results are set forth below in Table 7.

TABLE 7 Mechanical Properties of the Film Samples Mechanical PropertiesTime Needed Modulus Peak Stress Elongation to Disperse Sample No.Description Composition MD CD MD CD MD CD in Water Example 1 Glucosol800 starch/Sorbitol 70/30 740 196 29 5 6 6 10 Seconds Example 2 Elvanol51-05/Sorbitol 80/20 627 167 42 37 182 191 20 Seconds Example 3Celvol203/Sorbitol 80/20 841 521 45 45 225 186 30 Seconds Example 7Glucosol 800 TPS/p-Elvanol 51-05/Ecoflex 60/30/10 32 14 16 17 251 218 30Seconds Example 8 Glucosol 800 TPS/p-Elvanol 51-05/Ecoflex 70/20/10 7120 13 12 238 209 30 Seconds Example 9 Glucosol 800 TPS/p-Elvanol 51-0570/30 83 36 6 14 42 146 10 Seconds Example 10 Glucosol 800 TPS/p-Elvanol51-05/Ecoflex 63/27/10 64 20 17 18 239 218 1 Minute Example 11 Glucosol800 TPS/p-Elvanol 51-05/Ecoflex 56/24/20 29 34 16 17 254 228 1 MinuteExample 12 Glucosol 800 TPS/p-Elvanol 51-05/Ecoflex 49/21/30 23 41 19 21230 191 ~1 hour Example 13 Glucosol 800 TPS/Aquasol 116 70/30 44 11 1414 243 232 1 Minute Example 14 Glucosol 800 TPS/Aquasol 116/Ecoflex60/30/10 18 20 13 15 255 228 1 Minute Example 15 Glucosol 800TPS/Aquasol 116/Ecoflex 70/20/10 28 22 11 14 198 209 1½ Minute

As indicated, the film of Examples 1-3 (thermoplastic modified starch,plasticized Elvanol 51-05, and Celvol 203) were brittle as indicated bytheir high modulus values. The elongation for the film of Example 1(thermoplastic modified starch film) was particularly low in comparisonto those in Example 2 and 3 (plasticized PVA). The films of Example 7,8, 10˜12 (contained Ecoflex®) likewise had a low modulus and highelongation, i.e., above 200%. The film peak stress was very close toeach other among the different films. The films of Example 13˜15(containing Aqua-Sol™ 116) had a lower modulus than those shown inExample 7˜9, while the elongations values were comparable. Furthermore,as also indicated in Table 7, each of the film samples visiblydisintegrated in tap water in less than 1½ minute except for Example 12,which took about 60 minutes for the film to disperse in water.

While the invention has been described in detail with respect to thespecific embodiments thereof, it will be appreciated that those skilledin the art, upon attaining an understanding of the foregoing, mayreadily conceive of alterations to, variations of, and equivalents tothese embodiments. Accordingly, the scope of the present inventionshould be assessed as that of the appended claims and any equivalentsthereto.

1. A water-sensitive biodegradable film, the film comprising: from about1 wt. % to about 50 wt. % of at least one biodegradable polyester,wherein the biodegradable polyester has a melting point of from about50° C. to about 180° C. and a glass transition temperature of about 25°C. or less; from about 0.5 wt. % to about 45 wt. % of at least onewater-sensitive starch; from about 0.1 wt. % to about 40 wt. % of atleast one plasticizer; and from about 0.1 wt. % to about 40 wt. % of atleast one water-soluble polymer.
 2. The water-sensitive biodegradablefilm of claim 1, wherein the biodegradable polyester is an aliphaticpolyester, aliphatic-aromatic polyester, or a combination thereof. 3.The water-sensitive biodegradable film of claim 1, wherein thebiodegradable polyester is an aliphatic-aromatic copolyester.
 4. Thewater-sensitive biodegradable film of claim 1, wherein the biodegradablepolyester has a glass transition temperature of about 0° C. or less. 5.The water-sensitive biodegradable film of claim 1, wherein thebiodegradable polyester has a melting point of about 80° C. to about160° C.
 6. The water-sensitive biodegradable film of claim 1, whereinthe biodegradable polyester constitutes from about 5 wt. % to about 35wt. % of the film.
 7. The water-sensitive biodegradable film of claim 1,wherein the starch constitutes from about 10 wt. % to about 30 wt. % ofthe film.
 8. The water-sensitive biodegradable film of claim 1, whereinthe plasticizer constitutes from about 5 wt. % to about 30 wt. % of thefilm.
 9. The water-sensitive biodegradable film of claim 1, wherein thewater-soluble polymer constitutes from about 5 wt. % to about 30 wt. %of the film.
 10. The water-sensitive biodegradable film of claim 1,wherein the starch is a modified starch.
 11. The water-sensitivebiodegradable film of claim 10, wherein the modified starch is a starchester, starch ether, oxidized starch, hydrolyzed starch, or acombination thereof.
 12. The water-sensitive biodegradable film of claim10, wherein the modified starch is a hydroxylalkyl starch.
 13. Thewater-sensitive biodegradable film of claim 12, wherein the hydroxyalkylstarch is hydroxyethyl starch, hydroxypropyl starch, hydroxybutylstarch, or a combination thereof.
 14. The water-sensitive biodegradablefilm of claim 1, wherein the plasticizer is a polyhydric alcohol. 15.The water-sensitive biodegradable film of claim 14, wherein theplasticizer is a sugar alcohol.
 16. The water-sensitive biodegradablefilm of claim 1, wherein the water-soluble polymer includes vinylpyrrolidone, hydroxyethyl acrylate or methacrylate, hydroxypropylacrylate or methacrylate, acrylic or methacrylic acid, acrylic ormethacrylic esters or vinyl pyridine, acrylamide, vinyl acetate, vinylalcohol, ethylene oxide, or a combination thereof.
 17. Thewater-sensitive biodegradable film of claim 1, wherein the water-solublepolymer is a vinyl alcohol polymer.
 18. The water-sensitivebiodegradable film of claim 17, wherein the vinyl alcohol polymer has adegree of hydrolysis of from about 80 mole % to about 90 mole %.
 19. Thewater-sensitive biodegradable film of claim 1, wherein the film has athickness of about 50 micrometers or less.
 20. The water-sensitivebiodegradable film of claim 1, wherein the film exhibits a dry ultimatetensile strength of from about 10 to about 80 Megapascals in the machinedirection and a dry modulus of elasticity of from about 50 to about 1200Megapascals in the machine direction.
 21. The water-sensitivebiodegradable film of claim 1, wherein the film exhibits a dry ultimatetensile strength of from about 2 to about 40 Megapascals in thecross-machine direction and a dry modulus of elasticity of from about 50to about 1000 Megapascals in the cross-machine direction.
 22. Thewater-sensitive biodegradable film of claim 1, wherein the film exhibitsan elongation of about 50% or more in the machine direction and about50% or more in the cross-machine direction.
 23. The water-sensitivebiodegradable film of claim 1, wherein the film exhibits an elongationof about 100% or more in the machine direction and about 100% or more inthe cross-machine direction.
 24. A release liner comprising thewater-sensitive biodegradable film of claim 1 and a release agent coatedonto a surface thereof.
 25. An absorbent article comprising thewater-sensitive biodegradable film of claim 1, wherein the absorbentarticle comprises a body portion that includes a liquid permeabletopsheet, a generally liquid impermeable backsheet, and an absorbentcore positioned between the backsheet and the topsheet.
 26. Theabsorbent article of claim 25, wherein the backsheet includes thewater-sensitive biodegradable film.
 27. The absorbent article of claim25, further comprising a release liner that defines a first surface andan opposing second surface, the first surface being disposed adjacent toan adhesive located on the absorbent article, wherein the release linerincludes the water-sensitive biodegradable film.
 28. A pouch, wrap, orbag comprising the water-sensitive biodegradable film of claim
 1. 29-48.(canceled)